In the construction of shelf units, formation of slots of the desired width for insertion of the shelving has in the past been quite tedious and time-consuming for the carpenter. The shelf sections often vary slightly in thickness and accurate measurement is required to assure that each slot is formed of a width to assure tight-fitting insertion of the shelf board. Moreover, in forming a series of slots in the side wall supports for the shelving unit, it is important that the desired spacing be established between slots, and again, each slot must be of a specific desired width for tight-fitting insertion of each shelf board; further, the slot should be accurately squared with respect to the length of the board so as to assure accurate alignment of the shelf sections in spaced parallel relation to one another.
It is therefore highly desirable that a jig be provided for use by a carpenter which will serve as an aid in quickly and accurately forming slots of the desired width in the end panels or wall supports of a shelf unit which is portable, lightweight, simplified in construction and easy to use. Moreover, it is desirable that the jig be so constructed and arranged as to permit advancement of the board to be slotted into position, clamped down, and a slot of the desired width formed by insertion of a router with guide bushing through an adjustable guide opening provided in the jig wherein the width of the guide opening is set by the thickness of the board to be inserted in the slot.